Editing Ray tracing (graphics) (section)

===Recursive ray tracing algorithm===
[[File:Glasses 800 edit.png|right|thumb|300px|Ray tracing can create photorealistic images.]]
[[File:BallsRender.png|right|thumb|300px|In addition to the high degree of realism, ray tracing can simulate the [[Camera#Mechanics|effects of a camera]] due to [[depth of field]] and [[aperture]] shape (in this case a [[hexagon]]).]]
[[File:Ray-traced steel balls.jpg|right|thumb|300px|The number of reflections, or bounces, a "ray" can make, and how it is affected each time it encounters a surface, is controlled by settings in the software. In this image, each ray was allowed to reflect up to 16 times. Multiple "reflections of reflections" can thus be seen in these spheres. (Image created with [[Cobalt (CAD program)|Cobalt]].)]]
[[File:Glass ochem.png|right|thumb|300px|The number of [[refraction]]s a “ray” can make, and how it is affected each time it encounters a surface that permits the [[Transparency and translucency|transmission of light]], is controlled by settings in the software. Here, each ray was set to refract or reflect (the "depth") ''up to 9 times''. [[Fresnel reflection]]s were used and [[Caustic (optics)|caustics]] are visible. (Image created with [[V-Ray]].)]]

Earlier algorithms traced rays from the eye into the scene until they hit an object, but determined the ray color without recursively tracing more rays. Recursive ray tracing continues the process. When a ray hits a surface, additional rays may be cast because of reflection, refraction, and shadow.:<ref>{{cite journal | url = https://dip.felk.cvut.cz/browse/pdfcache/nikodtom_2010bach.pdf | title = Ray Tracing Algorithm For Interactive Applications | author = Tomas Nikodym | journal = Czech Technical University, FEE | date = June 2010 | archive-url = https://web.archive.org/web/20160303180450/https://dip.felk.cvut.cz/browse/pdfcache/nikodtom_2010bach.pdf | archive-date = March 3, 2016 }}</ref>
* A reflection ray is traced in the mirror-reflection direction. The closest object it intersects is what will be seen in the reflection.
*A refraction ray traveling through transparent material works similarly, with the addition that a refractive ray could be entering or exiting a material. [[Turner Whitted]] extended the mathematical logic for rays passing through a transparent solid to include the effects of refraction.<ref>{{cite book |last=Whitted |first=T. |year=1979 |chapter=An Improved Illumination Model for Shaded Display |title=Proceedings of the 6th annual conference on Computer graphics and interactive techniques |publisher=Association for Computing Machinery |citeseerx=10.1.1.156.1534 |isbn=0-89791-004-4 |chapter-url=http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.156.1534 }}</ref>
* A shadow ray is traced toward each light. If any opaque object is found between the surface and the light, the surface is in shadow and the light does not illuminate it.
These recursive rays add more realism to ray traced images.